Simulating Pliocene warmth and a permanent El Nino-like state; the role of cloud albedo

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doi: 10.1002/2014PA002644
Author(s): Burls, N. J.; Fedorov, A. V.
Author Affiliation(s): Primary:
Yale University, Department of Geology and Geophysics, New Haven, CT, United States
Volume Title: Paleoceanography
Source: Paleoceanography, 29(10), p.893-910. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 CODEN: POCGEP
Note: In English. NSF Grant AGS-1405272. 68 refs.; illus., incl. 3 tables
Summary: Available evidence suggests that during the early Pliocene (4-5 Ma) the mean east-west sea surface temperature (SST) gradient in the equatorial Pacific Ocean was significantly smaller than today, possibly reaching only 1-2°C. The meridional SST gradients were also substantially weaker, implying an expanded ocean warm pool in low latitudes. Subsequent global cooling led to the establishment of the stronger, modern temperature gradients. Given our understanding of the physical processes that maintain the present-day cold tongue in the east, warm pool in the west and hence sharp temperature contrasts, determining the key factors that maintained early Pliocene climate still presents a challenge for climate theories and models. This study demonstrates how different cloud properties could provide a solution. We show that a reduction in the meridional gradient in cloud albedo can sustain reduced meridional and zonal SST gradients, an expanded warm pool and warmer thermal stratification in the ocean, and weaker Hadley and Walker circulations in the atmosphere. Having conducted a range of hypothetical modified cloud albedo experiments, we arrive at our Pliocene simulation, which shows good agreement with proxy SST data from major equatorial and coastal upwelling regions, the tropical warm pool, middle and high latitudes, and available subsurface temperature data. As suggested by the observations, the simulated Pliocene-like climate sustains a robust El Nino-Southern Oscillation despite the reduced mean east-west SST gradient. Our results demonstrate that cloud albedo changes may be a critical element of Pliocene climate and that simulating the meridional SST gradient correctly is central to replicating the geographical patterns of Pliocene warmth. Abstract Copyright (2014), . American Geophysical Union. All Rights Reserved.
Year of Publication: 2014
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
ODP Ocean Drilling Program
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; Albedo; Atlantic Ocean; Atmospheric circulation; Atmospheric precipitation; Cape Basin; Ceara Rise; Cenozoic; Clouds; Cocos Ridge; Community Earth System Model; DSDP Site 214; DSDP Site 590; DSDP Site 607; Deep Sea Drilling Project; East Pacific; El Nino Southern Oscillation; Equatorial Atlantic; Equatorial Pacific; Exmouth Plateau; IPOD; Indian Ocean; Leg 115; Leg 122; Leg 130; Leg 138; Leg 154; Leg 159T; Leg 167; Leg 175; Leg 198; Leg 202; Leg 22; Leg 90; Leg 94; Lord Howe Rise; Lower Pliocene; Mid-Atlantic Ridge; Nazca Ridge; Neogene; Ninetyeast Ridge; North Atlantic; North Pacific; Northeast Atlantic; Northeast Pacific; Northwest Pacific; Numerical models; ODP Site 1010; ODP Site 1014; ODP Site 1021; ODP Site 1084; ODP Site 1208; ODP Site 1237; ODP Site 1241; ODP Site 709; ODP Site 763; ODP Site 806; ODP Site 846; ODP Site 847; ODP Site 848; ODP Site 849; ODP Site 850; ODP Site 853; ODP Site 925; ODP Site 958; Ocean Drilling Program; Ontong Java Plateau; Pacific Ocean; Paleoclimatology; Paleotemperature; Pliocene; Sea-surface temperature; Shatsky Rise; South Atlantic; South Pacific; Southeast Pacific; Southwest Pacific; Tertiary; West Pacific; Winds
Coordinates: S030548 N111326 W0902851 W1103419
N001906 N001907 E1592142 E1592140
S035454 S035454 E0603306 E0603306
S130652 S130650 E0612216 E0612215
Record ID: 2015004441
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom